This invention relates to a package comprising a stack of flexible light-sensitive sheet material.
It is difficult to pack stacks of sheets of light-sensitive material such as sheets of X-ray film material to ensure that during transportation of the stack there is no movement of the sheets relative to each other. Such relative movement cause scratching or marking of the surfaces of the sheet material if any particulate material such as dust is entrapped between the sheets of the stack. Such surface scratching or marking effects the light-senstive emulsion, which is on the surface of the sheet and alters its sensitometric properties in such a way that, depending on the conditions, either a sensitised or desensitised spot is produced, resulting in either a black or a white spot on development of the material. As it is almost impossible to exclude dust completely from the atmosphere when packing sheet material, it is very important to lessen the scratching effect of entrapped dust particles by preventing the relative movement of the sheets in a stack. A relative movement of as little as one hundreth of an inch (one fourth of a millimeter) can cause each entrapped dust particle to produce a very noticeable black or white spot on the developed material.
In U.S. Pat. No. 3,720,035 there is described a method of packing a stack composed of a plurality of flexible sheets which comprises stacking the flexible sheets to form a stack having two opposed face surfaces and two pairs of opposed side surfaces which define the thickness of the stack, one side surface of each pair being adjacent to both side surfaces of the other pair, the face surfaces and side surfaces of the stack forming edges which terminate in four corners where the two face surfaces are joined by two adjacent side surfaces, positioning four corner pieces made of a strong material so as to embrace each of the four corners of the stack of flexible sheets over the full thickness of the stack and thus encircling a portion of each face surface and the adjacent side surfaces which make up each corner to form a snug fit thereon, placing a length of strapping material around the side surfaces of the thus formed pack so that the strapping material passes around each of the positioned corner pieces, placing the pack into a rigid box or box-like structure, the dimensions of which are so chosen that the pack fits snugly in the box or box-like structure, thereafter applying a tension to the length of strapping material so causing the corner pieces to pull into close contact with the stack of flexible sheets, and then joining the length of strapping material to form a tension band around the pack. The stack of flexible sheets can be a stack of light-sensitive material.
The stack of flexible sheet material has preferably superimposed on each of its two large faces a sheet of stiff cardboard of the like rigid material, of slightly smaller dimension than the stack of flexible sheet material.
The length of strapping material under tension thus prevents the individual sheets from moving relatively to each other, and the stack of sheet material can not buckle due to the presence of the rigid box-like structure around the pack.